The present invention relates to sensor-illumination systems and in particular to an intelligent machine vision sensor-illumination system for use in three-dimensional measurement of objects and assemblies of objects.
In the manufacture of parts and assemblies by processes such as stamping, extrusion, drawing and casting from materials such as sheet or bulk metal, plastic, film rubber and the like, it is often required that accurate dimensional measurements be performed either on-line as the manufacturing process operates upon the part or assembly, or off-line upon samples temporarily removed from the manaufacturing production line. In order to obtain economies of manufacturing and produce high quality products, it is necessary that measurements be made to ensure that dimensional tolerances are maintained. Such measurements must be made rapidly at many points on each produced part or assembly and in such a manner that the part or assembly itself is not touched or otherwise affected substantially by the measurement process itself. Measurements are often required to be performed which determine the position in three-dimensional space of certain identified points or features which exist on the manufactured part or assembly. Such points or features typically include edges, corners, holes, designated portions of a surface, studs and intersections of surfaces. Special and general purpose computers exist which are capable of determining such measurements from image data produced by sufficiently intelligent sensor-illuminator systems.
Presently available sensor-illuminator systems are typically subject to several shortcomings. For example, many systems are highly specialized and provide limited three-dimensional data, thus limiting their application. Other more sophisticated systems tend to be overly complex and large in physical size making practical use of such systems virtually impossible. In addition, these systems also suffer from the problem of producing such complex image data that the required computer processing time to assimilate the data becomes excessive, thus further restricting practical application.
It is therefore an object of the present invention to provide an intelligent sensor-illuminator system that is capable of exercising significant self-control and yet is extremely compact in physical size.
In addition, it is an object of the present invention to provide a sensor-illuminator system that produces a unique structural illumination pattern which results in the production of image signals which permit an attached machine vision computer to dimensionally measure and locate a wide variety of surfaces and shapes, including planar surfaces at any orientation, curvilinear surfaces, holes and protrusions.
It is a further object of the present invention to provide a completely self-contained sensor-illuminator system that has permanently stored therein calibration and identification data which permits ready replacement of a faulty unit without the need for generating new calibration data.
It is also an object of the present invention to provide an intelligent sensor-illuminator system for making three-dimensional measurements which provides sufficient image data to an attached machine vision computer for such purposes without imposing an unduly complex computational burden on the computer.
In general, the present invention comprises a completely self-contained intelligent machine vision sensor-illumination system which includes a laser source preferably positioned normal to the surface of the part or assemblage of parts to be inspected, for projecting onto the surface a structured illumination which in the preferred embodiment is in the form of a cross hair pattern. A solid-state sensor device precisely located within the unit at a perspective angle relative to the angle of illumination and associated electronics produce image signals representing the projection of the structured light pattern on the surface of the part or assembly as viewed from such perspective angle. Control circuitry within the unit transmits to an attached machine vision computer specific calibration data prestored in the unit which is usable by the computer to accurately determine the three-dimensional position and orientation of the illuminated part or assembly from the image signals. The present invention also preferably includes control and communication elements permitting economical and rapid operation of a large number of sensor units in conjunction with a single attached machine vision computer and control cable, and under highly variable conditions of object light reflectance, sensor to computer cable connection distance and specific measurement point specification.
Additional objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which :